Question

2.1+-7/8-(-1又5/6)+-5/7过程？

Answer 1

加一个负数，等于减去一个正数；减去一个负数，等于加上一个正数：
2.1+-7/8-(-1又5/6)+-5/7
=2.1-7/8+1又5/6-5/7
=21/10-7/8+11/6-5/7
10=2x5；8=2x2x2；6=2x3；7=7
它们的最小公倍数是 2x2x2x3x5x7=840
通分后计算：
21/10-7/8+11/6-5/7
=（1764-735+1540-600）/840
=1959/840
=2又279/840

Answer 2

2.1+-7/8-(一1又5/6)十-5/7二2.1-7/8+11/6-5/7二2又1/10-7/8+11/6二1又88/80-70/80+11/6二1又18/80+11/6二1又27/120+1又100/120二2又127/120二3又7/120

Answer 3

2.1-7/8+11/6-5/7
=2.1-21/24+44/24-5/7
=2.1+23/24-5/7
=2.1+161/168-120/168
=2.1+41/168
=2+1/10+41/168
=2+168/1680+410/1680
=2+578/1680
=2又289/840